• Journal of the Korean Society for Precision Engineering
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• v.12 no.3
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• pp.119-129
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• 1995

In this paper, the inclined endmilling process with a 3-axis machining center using inclined jigs is introduced for the purpose of reducing overall Dies/Molds machining time and improving the machining accuracies. In order to analyze the cutting mechanism of a given endmill more accurately, the unification of the cutting mechanism model of 3-different- kind endmills is carried out by using a nose radius as a parameter. By adding radial runouts as a parameter which influences on surface roughness, the superposition method which defines the effective cusp height superposing the cutter mark height and the conventional cusp height is advanced. And 3-D suface topography predicted in this paper looks like the surface normally observed in practice. Through machining experiments, the adequacy of the superposition method was confirmed.

• JSTS:Journal of Semiconductor Technology and Science
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• v.8 no.1
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• pp.46-50
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• 2008

The effect of physicochemical properties of solvents on the microstructure of polyvinyl carbazole (PVK) film for non-volatile polymer memory was investigated. For the solubilization of PVK molecules and the preparation of PVK films, four solvents with different physicochemical properties of the Hildebrand solubility parameter and vapor pressure were considered: chloroform, tetrahydrofuran (THF), 1,1,2,2-tetrachloroethane (TCE), and N,N-dimehtylformamide (DMF). The solubility of PVK molecules in the solvents was observed by ultravioletvisible spectroscopy. PVK molecules were observed to be more soluble in chloroform, with a low Hildebrand solubility parameter, than solvents with higher values. The aggregated size and micro-/nano-topographical properties of PVK films were characterized using optical and atomic force microscopes. The PVK film cast from chloroform exhibited enhanced surface roughness compared to that from TCE and DMF. It was also confirmed that the microstructure of PVK film has an effect on the performance of non-volatile polymer memory.

• International Journal of Highway Engineering
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• v.11 no.2
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• pp.167-174
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• 2009

The simulation of dynamic load was conducted based on surface profile on asphalt concrete pavement, vehicle speeds, and suspension types using a truck simulation program. The results of the simulated dynamic load based on different surface profile, vehicle speeds, and suspension types are analyzed. As pavement roughness and vehicle speed are increased, the dynamic load was increased. Walking beam suspension produces greater dynamic load than air spring suspension. Pavement damage index is calculated based on covariance of dynamic load and Paris-Erdogan fracture parameter, n which is based on creep compliance tests of asphalt mixtures used in Korea. The higher covariance of dynamic load, confidence level, and fracture parameter are used, the greater pavement damage index is obtained. Specification of pavement roughness can be developed in various vehicle speeds and asphalt mixtures, and pay factor can be determined after constructing asphalt concrete pavement using pavement damage concepts.

• Journal of the Korean Vacuum Society
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• v.7 no.2
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• pp.161-168
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• 1998

Reactive ion etching process for InGaAs/InP using the CH4/H2 high density inductively coupled plasma was investigated. The experimental design method proposed by Taguchi was utilized to cover the whole parameter range while maintaining reasonable number of actual experiments. Results showed that the ICP power mainly affects surface roughness and verticality of the sidewall, bias power does etch rate and verticality, CH4 gas concentraion does the verticality and etch rate, and the distance between the induction coil and specimen mostly affects the surface roughness. It was also observed that the chamber pressure is the dominant parameter for the etch rate and verticality of the sidewall. The optimum condition was ICP power 700W, bias power 150 W, 15% $CH_4$, 7.5 mTorr, and 14 cm distance, resulting in about 3 $\mu\textrm{m}$/hr etch rate with smooth surfaces and vertical mesa sidewalls.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.1
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• pp.41-46
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• 2003

In order to evaluate the sufficient etching time for successful bonding and also minimizing unnecessary mineral loss, the enamel surface roughness analysis was performed using confocal laser scanning microscopy. Sixty extracted sound human molar teeth were imbedded in the center of acrylic cylinder using self-curing clear resin exposing buccal surface, and then polished with series of SiC paper(220, 500, 800, 1000, 2000, 4000 grit). Each specimen was randomly assigned to six groups(N=10). 37% phosphoric acid was applied to the polished tooth surface for 10, 20, 30, 40, 50, 60 seconds respectively and washed with copious water. After the surface roughness analysis, five roughness parameters(Sa, Sq, Sz, Sdr, Ra) were statistically analysed by ANOVA and Duncan post hoc test. We found that the all five parameters had higher roughness value in 30 seconds etching time, especially parameter Sz showed the lowest value in 10 seconds etching time and the highest value in 30 seconds etching time compared with the other etching times(p<0.05).

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.4
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• pp.354-361
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• 2008

Cold rolled steel sheet for automotive was treated by Ar/$O_2$ atmospheric pressure plasma to improve the adhesive bonding strength. Through the contact angle test and calculation of surface free energy for cold rolled steel sheet, the changes of surface properties were investigated before and after plasma treatment. The contact angle was decreased and surface free energy was increased after plasma treatment. And the change of surface roughness and morphology were observed by AFM(Atomic Force Microscope). The surface roughness of steel sheet was slightly changed. Based on Taguchi method, single lap shear test was performed to investigate the effect of experimental parameter such as plasma power, treatment time and flow rate of $O_2$ gas. Results shows that the bonding strength of steel sheet treated in Ar/$O_2$ atmospheric pressure plasma was improved about 20% compared with untreated sheet.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.3
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• pp.316-325
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• 1986

Characteristics of fatigue crack propagation in martensite-ferrite duel phase steels have been investigated. In low .DELTA.K region, fatigue crack propagation resistance increases with increasing volume fraction of martensite, but the difference of crack propagation resistance resulted from the volume fraction decreases with increasing .DELTA.K. Also, threshold stress intensity factor range .DELTA.K$_{th}$ increases with increasing volume fraction of martensite, But fatigue crack propagation rates of dual-phase steels in terms of .DELTA.K$_{eff}$ are independent to volume fraction of martensite. These phenomena can be explained by the roughness induced crack closure due to crack deflection.n.n.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.7
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• pp.680-686
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• 2006

Tin oxide$(SnO_2)$ thin films were prepared on glass substrate by Plasma Enhanced Chemical Vapor Deposition (PECVD) method. $SnO_2$ thin films were prepared using gas mixture of dibutyltin diacetate as a precursor and oxygen as an oxidant at 275, 325, 375, $425^{\circ}C$, respectively as a function of deposition temperature. The XRD peaks corresponded to those of polycrystalline $SnO_2$, which is in the tetragonal system with a rutil-type structure. As the deposition temperature increased, the texture plane of $SnO_2$ changed from (200) plane to denser (211) and (110) planes. Lower deposition temperature and shorter deposition time led to decreasing surface roughness and electrical resistivity of the formed thin films at $325\sim425^{\circ}C$. The properties of $SnO_2$ films were critically affected by deposition temperature and time.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.1
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• pp.35-42
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• 2014

Recently, in industry field, many researchers are looking for ways to reduce the use of lubricant because of environmental and economical reasons. MQL lubrication is one of many lubrication technologies. The aim of this study is to evaluate the machinability considering lubrication methods and taper angles of workpieces for turning of SCM440. Workpieces of two shapes such as workpiece with and without taper angle are used. And two lubrication methods such as MQL and Wet have been considered. And cutting force and surface roughness are used as characteristic values. Cutting speed, feed rate, injection angle and distance are used as design parameters. The characteristic values were statistically analyzed by Taguchi method. From the results, main effects plot and importance of each parameter according to conditions are analyzed. Finally, this study has been suggested the optimum machining conditions according to the lubrication methods, machining conditions and shape of workpiece.

• Journal of the Korean Vacuum Society
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• v.8 no.4B
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• pp.541-547
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• 1999

Reactive ion etching process for InP using BCl3/O2/Ar high density inductively coupled plasma was investigated. The experimental design method proposed by the Taguchi was utilized to cover the whole parameter range while maintaining reasonable number of actual experiments. Results showed that the ICP power and the chamber pressure were the two dominant parameters affectsing etch results. It was also observed that the etch rate decreased and the surface roughness improved as the ICP power and the bias voltage increased and as the chamber pressure decreased. The Addition of oxygen to the gas mixture drastically improved surface roughness by suppressing the formation of the surface reaction product. The optimum condition was ICP power 600W, bias voltage -100V, 10% $O_2$, 6mTorr, and $180^{\circ}C$, resulting in about 0.15$\mu\textrm{m}$ etch rate with smooth surfaces and vertical mesa sidewalls Also, the maximum etch rate of abut 4.5 $\mu\textrm{m}$/min was obtained at the condition of ICP power 800W, bias voltage -150V, 15% $O_2$, 8mTorr and $160^{\circ}C$.